Flying machine



I. l. SIKORSKY FLYING MACHINE Nov. 10, 1925.

Filed March 9, 1923 V 55 j 11v VEN TOR Adi A TTORNE VI Patented Nov. 10, 1925.

To all whom it may cmwern:

bus members locate the machine may be used toprovide the correction as will be ap arent. Fixed sur- UNITED STATES reon'r. srxoasxx, 012' mew YORK, u. 2.:

name

Application filed March 9, 1923. Serial 1%. 628,854.

Be it known that I, Icon I. SIKORSKY, a citizen of Russia, residing in New York city, New York, have invented the following'described Improvements in Flying Machines.

An im ortant advantage of a multiple motored ying machine is its ability to continue flight with one or more ofthe' motors:

stopped. vAs is well-known, however, machines driven by a number of. propellers tend to veer when'one of the side propellers stops, or the motors driving the side propellers develop power unevenly so that the driving forces at the opposite sides of the machine are unbalanced The pilot can correctthis change in the direction of flight by shifting his rudders, but the liability of the machine to suddenly veer in this manner at any time during flight contains an element of danger, and furthermore, for the remainder of the flight the maneuverability of the machine is diminished and its control is more diflicult since 'a certain degree of inclination is required of the rudders, one way or the other, to compensate for the unbalanced driving forces. This is particularly true with respect to aeroplanes.

The object of my invention isto preserve the usual stability of way, maneuverability,

and ease of control under the adverse condL-l tions of asymmetrical propeller thrusts; in

other words, to eliminate or at least materially diminish the tendency of the machine to veer when the driving forces become unbalanced in the manner indicated. I accomfiplish this object by .meansof a rudder or system, or other system of surfaces, which is locatedmore or less in the air streams created by the propellers, the arrangement of the system being such that the propeller-created air flows, striking the system, cause the correcting system to produce a resultant turnin effort which is zero or neutral when the an flows are normal, but which tend to turn the machine in the correctin abnorma or unbalanced. Any and every unbalancing of propeller thrust is thus couna;

teracted automatically and simultaneously with the engine or (propeller failure. Variat various places about faces, for example, may used, or the usual arrangement, t

propeller) tend to"cause the machine to use or fall vertically or diagonally (accorddirection when the air flows are 7 cor'porating the preferred form .of the inrudders, or combinations of fixed surfaces and rudders may beemployed. Preferably the correcting members or surfaces are located 'well back of theengine in the slip streams flowing back from the propellers; so located, each surface is so shaped 01-1 positioned -(or'both) as to produce a force directed toward the center line of the machine under the thrust of the slip stream. A number of such arrangements are illustrated in the accompanying drawings. i

The invention is not only, a plicable to the usual placement of multip eengines and multiple propellers, that is to say, ,the arrangement in which thelpropellers are distributed at the ri ht and left of" the center l1ne of the machlne (with which arrangement the machinetends to turn to the right" or left when'the driving'forces are unbal-- anced), but it .is also applicable 1 to such other distributions of the propellers as bring -'some or all the propellers away from the machine center line. For example,-it maybe used with machines in which ropellers are placed one above another; wlth this latter failure of one engine (or ing to the. arrangement as a whole). intend to include all such applications of the invention within the claims which; follow and I intend the expression propefalle'rs'iarranged .at op osite sides of'the machine center line include arrangements of the propellers above or below the horizontal plane of the machine center line as well as strictly to the right and and similar expressions), to 1 left of the center line, except where'the contrary isdistinctly indicatedQ I The accompanying drawings "illustrate various forms of my invention particularly intended for aeroplanes having their procommonvat. the present. 7. time, namely, at the right and left [of the center line of the machine.

pellers placed 'in' the I manner which is 10o Fig. 1 is a diagram-.

matic plan view of such an aeroplane in- The elevating rudder or rudders 5 are attached to the tail in the Jusualmanner. The details of these parts are immaterial and the machine may be amonoplane or polyplane.

Three engines and propellers are shown and these are placed in the usual manner, one at the forward end of the fuselage at 8'-and another ateach side of the center lineof the machine at 9 and 10. The propeller of each engine is attached to the end of the engine shaft, one propeller being thus located at. U

augmented as will be understoodnixThe, cor I the right of the center line 14 of the ma: chine, one at the left and one'substantially in the centerline. The rudders 15 and 16 by which the machine is directed to. the right or the left have been reshaped and rearranged to add the present invention to their functions, that is to say, to minimize the tendency of the machine ,to veer either to the right or to the left when the thrust of either of the propellers of the side engines 9.- and 10 in any way become less than the thrust of the other. No'means are needed to similarly correct for. failure of propellers located like the propeller of engine 8 (that- 1 is to say, located in the center line 14 of the machine as stated) since failure of a pro-; 'peller thus located is unaccompanied by any 3 direct tendency of the. machine to veer .to the right or to the left." F ailure. of this en gine principally reduces the total power of the machine. Each of the rudders 15 and 16 is mounted, as usual, to. turn'about a vertical axis 17 on. the tail. In the customary manner also, the rear ends of these ma,

ders are coupled together as at 18 and flexible lines 19 .and 20- working on sectors fixed to the forward ends of the rudders connect the rudders to the pilots foot pedals21 and 22 res ectively, so that depression of one of these oot pedals turns-both rudders to the left or tothe right to ether. "In accordance with my invention,;th e rudders of this -system 15-f16 aredlocated in the slip streams of those propellers thataredisplaced from the center line (if the ma-- chine, that is to'say, the rtidder 15 is placed in. the backward flowing air stream created} 9 while the rudby the propeller of engme der '16 is similarly placed in the air stream flowing back from the propeller ,of engine :10. Furthermoraas shown, these rudders are so connected together by the connection Y18 and areso connected to the'foot pedals 21 and 22 as to be inclinedto these air streams in opposite directions whenin neutral position (that is to say for straight ahead flight), the rudder 15 at the left being so inclined as to tend to turn themachine to the left while the rudder 16 at the right is inclined to turn the machine to the right. The forward ends of both rudders 15 and 16 lean toward the center, line of the machine the therefore and each exerts a force toward the machine center. line Y (tending to turn the machine) whenthe system is'in neutral position. Furthermore, in this preferred form facesjfacing' toward the center line 14 of the machine and their fiat (or concave or less conyex) surfaces facing outw a'rdsh By reason q f thi's asymmetrlcal form," th6 for ces produced-myths rudders and directedtowardsfl'the center line of the ,machine-t-are' recting members may, however;

rical in form A (stream line or not pend solely ontheir inclination; toj the-line; I

of air attack for :their individual turning 'eiforts (Fig-,ja), or their normal" or neutral position-;may he'iparallel to the line of attack, their turning-efforts bein secured solely by anj asymmetrical form (l ig. 5).. I prefer, however, regardless of whether 'the correcting surfaces are control rudders or not, to employ both aldegree' of inclination and an asymmetrical cross'sectional' form to secure the. 'indiyidual'f correcting turning efforts-in so far as possible. Since the two rudders 1 5 and16 arealike and are opposed as to their turning efforts, under normal conditions the resultant or sum ofthe indi vidual turning efforts of the rudders of the system is zeroVor,- rather, neutral. That is to say, so long 'as the'- two engines 9 and 10 are exerting equal driving efforts in straight ahead flight and hence are producing like slip streams, the turning effort of the rudder 15 under the thrust. .of-Ithe left-hand slip stream is exactly-equal, and is opposed in direction'to the turning effort of the rudder sofa-r as it may afiectthe rudders) is likewise equal and opposed-on the two sides of system. When the pilot turns the rudders 15 and 16 to direct the machine to the right or to the left, the" centerwards efi'orts 16 finder the thrust 'of-fthe right-hand slip stream. The thrust'of the atmosphere (in ofthe two rudders may cease to be equal ,as will be 'apparent,' but the resultant or difference. between the two-efforts is in such a-"dir'ection asm to turn the; machine in the direction." the pilot desires to fly; The resnltant efiort therefore, of the inclination and asymmetrical form of the correcting surfaces, is neutral under all normal operating conditions, that'is to? say, when the I thrustsof the side propellers are symmetrlcal and balanced and in accordance with the design. 'When, however, one? of the side engines stops, say the engine 9, or this engine fails to deliver as much power as the opposing side engine 10, then the individual turn ing efforts of the two rudders no longer balance but the turning effort of the rudder 16 predominates. This is due to the fact that engine 10 to turn the machine to the left and accordingly the machine tends to continue to fly straight ahead (or to the right or left if the pilot has previously turned the rudders to the left or right) just as though both engines were in normal operation. the engine 9 continues its full effort causes the correcting system to exert a turning effort in the opposite direction as will be apparent. It is evident therefore that the Failure of the side motor 10 while' turning effort of asymmetrical thrust of the off-center propellers driven by the engines 9 and 10, is opposed by the initial inclination and asymmetrical form which I have given the rudders 15 and 16 (the latter, further, being placed within air currents'created by those propellers).- It is apparent that the correction is applied automatically and simultaneously with, and is proportional to the extent of the engine failure.

Maneuverability and ease of control are preserved therefore.

It will be seen from the foregoing that the underlying principles of my invention are that correcting surfaces are located'within the air streams created by those propellers which exert individual efforts on the machine to turn it from the line ,of flight and that these correcting surfaces are so arranged or constructed (or both) as .wto exert turning efforts on the machine (under the thrust or attack of the air flows), which are in such directions as tooppose the turn ing efforts of the propeller or'propellers which create the respective air-flows. Obvio'usly the number of correcting surfaces and their location with respect to the propellers may be varied to suit particular machines.

Preferably, however, they are locatedwithin the slip streams well to the rear of the propellers. It will also be understood that while two control rudders are preferably used to furnish the correcting surfaces, the

with reference to Fig. 1. Fig. 7 illustrates another example, fins 34 being fixed to the tail and serving solely to correct for asymmetrical propeller thrust. The center rudder' 35 in this figure takes no part in cor recting for unbalanced propeller thrust but acts solely to direct the flight of the machine at the will of the pilot. As before mentioned, the turning e orts are preferably obtained by combining some inclination of the correcting surfaces with an asymmetrical formand the fixed fins 34 are so inclined and shaped. The invention however is not limited to the forms. illustrated but it will be understood from the foregoing that still other embodiments of it may be devised.

Claims- 1. The combination with a flying machine having a number of propellers arranged at opposltesides of'the machine center line, of means providing surfaces to counteract the turningeifort'of unbalanced thrust of said propellers, said surfaces being located within air streams normally created by said propellers and each of saidsurfaces exerting a turning effort on the machine which opposes the turning effort of the ropeller or propellers which create the air stream within which the respective surface is located.

2. The combination with a flying machine having. a number of propellers arranged at opposite sides of the machine centerline, of

means providing aplurality of surfaces located within air streams normally created by said propellers and producing individual forces at an angle to the center line of the machine during straight-line flight, the resultant of said individual forces being neu-' tral under normal conditions;

:3. The combination with a flying machine having anumber of propellers arran' ed at opposite sides of the machine center line, of

meansproviding a system of correcting sur-,

faces to oppose the turning effort of unbalanced thrustof said propellers, said surfaces beinglocated at opposite sides of the center line of the machine and within the air correcting surfaces may be otherwise providedas before indicated. Fig. 6, illustrates a combination of control rudders 30 and fixed rudder fins 31, so arranged as to provide the correctingsurfaces. In this illustration each fin and ruddercombinat'ion is symmetrical in cross-section, the turning efforts being obtained solely by inclining the fins and rudders in themanner described streams normally created by said propellers and each individual surface being so mclined to its air stream. during straight line flight, that it produces a turning effort. on the machine opposing the turning eflort produced by the propeller or propellers creating the air stream in which the respective surface is located.

4. The combination with a flying machine having a number of propellers arranged at opposite sides of the machine center line, of a system of correcting members located at opposite sides of the machine within air streams normally created by said propellers,

each member being of such asymmetrical aerofoil form in'cross-section as to produce during straighteline flight a-turning effort on the machine opposing the turning effort of the propeller or propellers which create the air stream inwhich it is located.

5. The combination with a flying machine havin a number of propellers arranged at opposite sides of the machine center line, of a system of correcting members located at opposite sides of the center line ofsystem of control rudders .and means for shifting said rudders at will to direct the flight of the machine, characterized by the rudders being located within the slip-streams behind said propellers and so organized that each of said rudders roduces a force directed toward the machine center line during straight line flight under normal conditions and the resultant of said forces of the system being neutral under normal conditions.

7. A multi-engined flying machine having propellers arranged at the right and the left of the center line of the machine, a system of control rudders including vertical rudders to 1 direct the flight of the machine to the right and-the left, and means. for shifting said vertical rudders at will to direct the flight,

characterized by the said vertical rudders being located at the right and the left of the machine center line and in the slip streams behind said propellers, being of asymmetrical aerofoil form with the protuberant convex surfaces facing the machine center line, and bein inclined to the slip-streams in straight line flight, with their forward ends nearer the machine center line.

In testimony whereof, I have signed this specification.

IGOR I. SIKORSKY. 

